1 /* 2 * mm/mremap.c 3 * 4 * (C) Copyright 1996 Linus Torvalds 5 * 6 * Address space accounting code <alan@redhat.com> 7 * (C) Copyright 2002 Red Hat Inc, All Rights Reserved 8 */ 9 10 #include <linux/mm.h> 11 #include <linux/hugetlb.h> 12 #include <linux/slab.h> 13 #include <linux/shm.h> 14 #include <linux/mman.h> 15 #include <linux/swap.h> 16 #include <linux/capability.h> 17 #include <linux/fs.h> 18 #include <linux/highmem.h> 19 #include <linux/security.h> 20 #include <linux/syscalls.h> 21 #include <linux/mmu_notifier.h> 22 23 #include <asm/uaccess.h> 24 #include <asm/cacheflush.h> 25 #include <asm/tlbflush.h> 26 27 static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr) 28 { 29 pgd_t *pgd; 30 pud_t *pud; 31 pmd_t *pmd; 32 33 pgd = pgd_offset(mm, addr); 34 if (pgd_none_or_clear_bad(pgd)) 35 return NULL; 36 37 pud = pud_offset(pgd, addr); 38 if (pud_none_or_clear_bad(pud)) 39 return NULL; 40 41 pmd = pmd_offset(pud, addr); 42 if (pmd_none_or_clear_bad(pmd)) 43 return NULL; 44 45 return pmd; 46 } 47 48 static pmd_t *alloc_new_pmd(struct mm_struct *mm, unsigned long addr) 49 { 50 pgd_t *pgd; 51 pud_t *pud; 52 pmd_t *pmd; 53 54 pgd = pgd_offset(mm, addr); 55 pud = pud_alloc(mm, pgd, addr); 56 if (!pud) 57 return NULL; 58 59 pmd = pmd_alloc(mm, pud, addr); 60 if (!pmd) 61 return NULL; 62 63 if (!pmd_present(*pmd) && __pte_alloc(mm, pmd, addr)) 64 return NULL; 65 66 return pmd; 67 } 68 69 static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd, 70 unsigned long old_addr, unsigned long old_end, 71 struct vm_area_struct *new_vma, pmd_t *new_pmd, 72 unsigned long new_addr) 73 { 74 struct address_space *mapping = NULL; 75 struct mm_struct *mm = vma->vm_mm; 76 pte_t *old_pte, *new_pte, pte; 77 spinlock_t *old_ptl, *new_ptl; 78 unsigned long old_start; 79 80 old_start = old_addr; 81 mmu_notifier_invalidate_range_start(vma->vm_mm, 82 old_start, old_end); 83 if (vma->vm_file) { 84 /* 85 * Subtle point from Rajesh Venkatasubramanian: before 86 * moving file-based ptes, we must lock vmtruncate out, 87 * since it might clean the dst vma before the src vma, 88 * and we propagate stale pages into the dst afterward. 89 */ 90 mapping = vma->vm_file->f_mapping; 91 spin_lock(&mapping->i_mmap_lock); 92 if (new_vma->vm_truncate_count && 93 new_vma->vm_truncate_count != vma->vm_truncate_count) 94 new_vma->vm_truncate_count = 0; 95 } 96 97 /* 98 * We don't have to worry about the ordering of src and dst 99 * pte locks because exclusive mmap_sem prevents deadlock. 100 */ 101 old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl); 102 new_pte = pte_offset_map_nested(new_pmd, new_addr); 103 new_ptl = pte_lockptr(mm, new_pmd); 104 if (new_ptl != old_ptl) 105 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); 106 arch_enter_lazy_mmu_mode(); 107 108 for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE, 109 new_pte++, new_addr += PAGE_SIZE) { 110 if (pte_none(*old_pte)) 111 continue; 112 pte = ptep_clear_flush(vma, old_addr, old_pte); 113 pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr); 114 set_pte_at(mm, new_addr, new_pte, pte); 115 } 116 117 arch_leave_lazy_mmu_mode(); 118 if (new_ptl != old_ptl) 119 spin_unlock(new_ptl); 120 pte_unmap_nested(new_pte - 1); 121 pte_unmap_unlock(old_pte - 1, old_ptl); 122 if (mapping) 123 spin_unlock(&mapping->i_mmap_lock); 124 mmu_notifier_invalidate_range_end(vma->vm_mm, old_start, old_end); 125 } 126 127 #define LATENCY_LIMIT (64 * PAGE_SIZE) 128 129 unsigned long move_page_tables(struct vm_area_struct *vma, 130 unsigned long old_addr, struct vm_area_struct *new_vma, 131 unsigned long new_addr, unsigned long len) 132 { 133 unsigned long extent, next, old_end; 134 pmd_t *old_pmd, *new_pmd; 135 136 old_end = old_addr + len; 137 flush_cache_range(vma, old_addr, old_end); 138 139 for (; old_addr < old_end; old_addr += extent, new_addr += extent) { 140 cond_resched(); 141 next = (old_addr + PMD_SIZE) & PMD_MASK; 142 if (next - 1 > old_end) 143 next = old_end; 144 extent = next - old_addr; 145 old_pmd = get_old_pmd(vma->vm_mm, old_addr); 146 if (!old_pmd) 147 continue; 148 new_pmd = alloc_new_pmd(vma->vm_mm, new_addr); 149 if (!new_pmd) 150 break; 151 next = (new_addr + PMD_SIZE) & PMD_MASK; 152 if (extent > next - new_addr) 153 extent = next - new_addr; 154 if (extent > LATENCY_LIMIT) 155 extent = LATENCY_LIMIT; 156 move_ptes(vma, old_pmd, old_addr, old_addr + extent, 157 new_vma, new_pmd, new_addr); 158 } 159 160 return len + old_addr - old_end; /* how much done */ 161 } 162 163 static unsigned long move_vma(struct vm_area_struct *vma, 164 unsigned long old_addr, unsigned long old_len, 165 unsigned long new_len, unsigned long new_addr) 166 { 167 struct mm_struct *mm = vma->vm_mm; 168 struct vm_area_struct *new_vma; 169 unsigned long vm_flags = vma->vm_flags; 170 unsigned long new_pgoff; 171 unsigned long moved_len; 172 unsigned long excess = 0; 173 unsigned long hiwater_vm; 174 int split = 0; 175 176 /* 177 * We'd prefer to avoid failure later on in do_munmap: 178 * which may split one vma into three before unmapping. 179 */ 180 if (mm->map_count >= sysctl_max_map_count - 3) 181 return -ENOMEM; 182 183 new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT); 184 new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff); 185 if (!new_vma) 186 return -ENOMEM; 187 188 moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len); 189 if (moved_len < old_len) { 190 /* 191 * On error, move entries back from new area to old, 192 * which will succeed since page tables still there, 193 * and then proceed to unmap new area instead of old. 194 */ 195 move_page_tables(new_vma, new_addr, vma, old_addr, moved_len); 196 vma = new_vma; 197 old_len = new_len; 198 old_addr = new_addr; 199 new_addr = -ENOMEM; 200 } 201 202 /* Conceal VM_ACCOUNT so old reservation is not undone */ 203 if (vm_flags & VM_ACCOUNT) { 204 vma->vm_flags &= ~VM_ACCOUNT; 205 excess = vma->vm_end - vma->vm_start - old_len; 206 if (old_addr > vma->vm_start && 207 old_addr + old_len < vma->vm_end) 208 split = 1; 209 } 210 211 /* 212 * If we failed to move page tables we still do total_vm increment 213 * since do_munmap() will decrement it by old_len == new_len. 214 * 215 * Since total_vm is about to be raised artificially high for a 216 * moment, we need to restore high watermark afterwards: if stats 217 * are taken meanwhile, total_vm and hiwater_vm appear too high. 218 * If this were a serious issue, we'd add a flag to do_munmap(). 219 */ 220 hiwater_vm = mm->hiwater_vm; 221 mm->total_vm += new_len >> PAGE_SHIFT; 222 vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT); 223 224 if (do_munmap(mm, old_addr, old_len) < 0) { 225 /* OOM: unable to split vma, just get accounts right */ 226 vm_unacct_memory(excess >> PAGE_SHIFT); 227 excess = 0; 228 } 229 mm->hiwater_vm = hiwater_vm; 230 231 /* Restore VM_ACCOUNT if one or two pieces of vma left */ 232 if (excess) { 233 vma->vm_flags |= VM_ACCOUNT; 234 if (split) 235 vma->vm_next->vm_flags |= VM_ACCOUNT; 236 } 237 238 if (vm_flags & VM_LOCKED) { 239 mm->locked_vm += new_len >> PAGE_SHIFT; 240 if (new_len > old_len) 241 make_pages_present(new_addr + old_len, 242 new_addr + new_len); 243 } 244 245 return new_addr; 246 } 247 248 /* 249 * Expand (or shrink) an existing mapping, potentially moving it at the 250 * same time (controlled by the MREMAP_MAYMOVE flag and available VM space) 251 * 252 * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise 253 * This option implies MREMAP_MAYMOVE. 254 */ 255 unsigned long do_mremap(unsigned long addr, 256 unsigned long old_len, unsigned long new_len, 257 unsigned long flags, unsigned long new_addr) 258 { 259 struct mm_struct *mm = current->mm; 260 struct vm_area_struct *vma; 261 unsigned long ret = -EINVAL; 262 unsigned long charged = 0; 263 264 if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE)) 265 goto out; 266 267 if (addr & ~PAGE_MASK) 268 goto out; 269 270 old_len = PAGE_ALIGN(old_len); 271 new_len = PAGE_ALIGN(new_len); 272 273 /* 274 * We allow a zero old-len as a special case 275 * for DOS-emu "duplicate shm area" thing. But 276 * a zero new-len is nonsensical. 277 */ 278 if (!new_len) 279 goto out; 280 281 /* new_addr is only valid if MREMAP_FIXED is specified */ 282 if (flags & MREMAP_FIXED) { 283 if (new_addr & ~PAGE_MASK) 284 goto out; 285 if (!(flags & MREMAP_MAYMOVE)) 286 goto out; 287 288 if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len) 289 goto out; 290 291 /* Check if the location we're moving into overlaps the 292 * old location at all, and fail if it does. 293 */ 294 if ((new_addr <= addr) && (new_addr+new_len) > addr) 295 goto out; 296 297 if ((addr <= new_addr) && (addr+old_len) > new_addr) 298 goto out; 299 300 ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1); 301 if (ret) 302 goto out; 303 304 ret = do_munmap(mm, new_addr, new_len); 305 if (ret) 306 goto out; 307 } 308 309 /* 310 * Always allow a shrinking remap: that just unmaps 311 * the unnecessary pages.. 312 * do_munmap does all the needed commit accounting 313 */ 314 if (old_len >= new_len) { 315 ret = do_munmap(mm, addr+new_len, old_len - new_len); 316 if (ret && old_len != new_len) 317 goto out; 318 ret = addr; 319 if (!(flags & MREMAP_FIXED) || (new_addr == addr)) 320 goto out; 321 old_len = new_len; 322 } 323 324 /* 325 * Ok, we need to grow.. or relocate. 326 */ 327 ret = -EFAULT; 328 vma = find_vma(mm, addr); 329 if (!vma || vma->vm_start > addr) 330 goto out; 331 if (is_vm_hugetlb_page(vma)) { 332 ret = -EINVAL; 333 goto out; 334 } 335 /* We can't remap across vm area boundaries */ 336 if (old_len > vma->vm_end - addr) 337 goto out; 338 if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)) { 339 if (new_len > old_len) 340 goto out; 341 } 342 if (vma->vm_flags & VM_LOCKED) { 343 unsigned long locked, lock_limit; 344 locked = mm->locked_vm << PAGE_SHIFT; 345 lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur; 346 locked += new_len - old_len; 347 ret = -EAGAIN; 348 if (locked > lock_limit && !capable(CAP_IPC_LOCK)) 349 goto out; 350 } 351 if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT)) { 352 ret = -ENOMEM; 353 goto out; 354 } 355 356 if (vma->vm_flags & VM_ACCOUNT) { 357 charged = (new_len - old_len) >> PAGE_SHIFT; 358 if (security_vm_enough_memory(charged)) 359 goto out_nc; 360 } 361 362 /* old_len exactly to the end of the area.. 363 * And we're not relocating the area. 364 */ 365 if (old_len == vma->vm_end - addr && 366 !((flags & MREMAP_FIXED) && (addr != new_addr)) && 367 (old_len != new_len || !(flags & MREMAP_MAYMOVE))) { 368 unsigned long max_addr = TASK_SIZE; 369 if (vma->vm_next) 370 max_addr = vma->vm_next->vm_start; 371 /* can we just expand the current mapping? */ 372 if (max_addr - addr >= new_len) { 373 int pages = (new_len - old_len) >> PAGE_SHIFT; 374 375 vma_adjust(vma, vma->vm_start, 376 addr + new_len, vma->vm_pgoff, NULL); 377 378 mm->total_vm += pages; 379 vm_stat_account(mm, vma->vm_flags, vma->vm_file, pages); 380 if (vma->vm_flags & VM_LOCKED) { 381 mm->locked_vm += pages; 382 make_pages_present(addr + old_len, 383 addr + new_len); 384 } 385 ret = addr; 386 goto out; 387 } 388 } 389 390 /* 391 * We weren't able to just expand or shrink the area, 392 * we need to create a new one and move it.. 393 */ 394 ret = -ENOMEM; 395 if (flags & MREMAP_MAYMOVE) { 396 if (!(flags & MREMAP_FIXED)) { 397 unsigned long map_flags = 0; 398 if (vma->vm_flags & VM_MAYSHARE) 399 map_flags |= MAP_SHARED; 400 401 new_addr = get_unmapped_area(vma->vm_file, 0, new_len, 402 vma->vm_pgoff, map_flags); 403 if (new_addr & ~PAGE_MASK) { 404 ret = new_addr; 405 goto out; 406 } 407 408 ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1); 409 if (ret) 410 goto out; 411 } 412 ret = move_vma(vma, addr, old_len, new_len, new_addr); 413 } 414 out: 415 if (ret & ~PAGE_MASK) 416 vm_unacct_memory(charged); 417 out_nc: 418 return ret; 419 } 420 421 asmlinkage unsigned long sys_mremap(unsigned long addr, 422 unsigned long old_len, unsigned long new_len, 423 unsigned long flags, unsigned long new_addr) 424 { 425 unsigned long ret; 426 427 down_write(¤t->mm->mmap_sem); 428 ret = do_mremap(addr, old_len, new_len, flags, new_addr); 429 up_write(¤t->mm->mmap_sem); 430 return ret; 431 } 432